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Allow zone terminal unit HW coil UA sizing failure to proceed when using ReverseWithLimit in heating dominated climates #11079

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Allow zone terminal unit HW coil UA sizing failure to proceed when using ReverseWithLimit in heating dominated climates #11079

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8fdd5b0
Allow HW coil UA sizing failure to proceed
rraustad May 22, 2025
a81ec44
Fix failed unit tests
rraustad May 22, 2025
a94af4e
Add check for this->DamperHeatingAction == Action::ReverseWithLimits
rraustad May 22, 2025
0ab8445
Rework conditionals to relax unit test requirements
rraustad May 22, 2025
134fa7a
Merge branch 'develop' of https://github.com/NREL/EnergyPlus into 110…
rraustad Sep 16, 2025
b232a09
Add more information to new warning message
rraustad Sep 16, 2025
ffec3a1
Fix units in warning message
rraustad Sep 16, 2025
eb0e298
Merge branch 'develop' into 11078-VAV-ReheatCoil-UASizing-failure
mitchute Oct 31, 2025
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10 changes: 2 additions & 8 deletions src/EnergyPlus/Autosizing/WaterHeatingCoilUASizing.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -82,7 +82,6 @@ Real64 WaterHeatingCoilUASizer::size(EnergyPlusData &state, Real64 _originalValu
};
General::SolveRoot(state, Acc, MaxIte, SolFla, this->autoSizedValue, f, UA0, UA1);
if (SolFla == -1) {
errorsFound = true;
std::string msg = "Autosizing of heating coil UA failed for Coil:Heating:Water \"" + this->compName + "\"";
this->addErrorMessage(msg);
ShowSevereError(state, msg);
Expand Down Expand Up @@ -141,10 +140,7 @@ Real64 WaterHeatingCoilUASizer::size(EnergyPlusData &state, Real64 _originalValu
this->addErrorMessage(msg);
ShowContinueError(state, msg);
}
this->dataErrorsFound = true;
} else if (SolFla == -2) {
this->errorType = AutoSizingResultType::ErrorType1;
errorsFound = true;
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@rraustad rraustad May 22, 2025

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Failed SolveRoot with a -1 for iterations exceeded or -2 for bad limits are now not an error but instead a diagnostic, with messages and sizing data to aid the user in a resolution,

std::string msg = "Autosizing of heating coil UA failed for Coil:Heating:Water \"" + this->compName + "\"";
this->addErrorMessage(msg);
ShowSevereError(state, msg);
Expand Down Expand Up @@ -217,7 +213,7 @@ Real64 WaterHeatingCoilUASizer::size(EnergyPlusData &state, Real64 _originalValu
this->addErrorMessage(msg);
ShowContinueError(state, msg);
}
this->dataErrorsFound = true;
this->autoSizedValue = UA1;
}
} else {
this->autoSizedValue = 1.0;
Expand Down Expand Up @@ -258,7 +254,6 @@ Real64 WaterHeatingCoilUASizer::size(EnergyPlusData &state, Real64 _originalValu
};
General::SolveRoot(state, Acc, MaxIte, SolFla, this->autoSizedValue, f, UA0, UA1);
if (SolFla == -1) {
errorsFound = true;
std::string msg = "Autosizing of heating coil UA failed for Coil:Heating:Water \"" + this->compName + "\"";
this->addErrorMessage(msg);
ShowSevereError(state, msg);
Expand Down Expand Up @@ -301,7 +296,6 @@ Real64 WaterHeatingCoilUASizer::size(EnergyPlusData &state, Real64 _originalValu
this->addErrorMessage(msg);
ShowContinueError(state, msg);
}
this->dataErrorsFound = true;
} else if (SolFla == -2) {
this->errorType = AutoSizingResultType::ErrorType1;
errorsFound = true;
Expand Down Expand Up @@ -361,7 +355,7 @@ Real64 WaterHeatingCoilUASizer::size(EnergyPlusData &state, Real64 _originalValu
this->addErrorMessage(msg);
ShowContinueError(state, msg);
}
this->dataErrorsFound = true;
this->autoSizedValue = UA1;
}
} else {
this->autoSizedValue = 1.0;
Expand Down
38 changes: 37 additions & 1 deletion src/EnergyPlus/SingleDuct.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -3000,7 +3000,43 @@ void SingleDuctAirTerminal::SizeSys(EnergyPlusData &state)
}
}
}

if (state.dataSize->TermUnitFinalZoneSizing.size() > 0 && this->DamperHeatingAction == Action::ReverseWithLimits &&
TermUnitSizing(state.dataSize->CurTermUnitSizingNum).AirVolFlow <
state.dataSize->TermUnitFinalZoneSizing(state.dataSize->CurTermUnitSizingNum).DesHeatVolFlow) {
ShowMessage(state, format("SizeHVACSingleDuct: Potential issue with equipment sizing for {} = \"{}\".", this->sysType, this->SysName));
ShowContinueError(state,
format("Terminal unit design air flow rate during Reheat of {:.5R} [m3/s]",
TermUnitSizing(state.dataSize->CurTermUnitSizingNum).AirVolFlow));
ShowContinueError(state,
format("is less than the zone design heating air flow rate of {:.5R} [m3/s]",
state.dataSize->TermUnitFinalZoneSizing(state.dataSize->CurTermUnitSizingNum).DesHeatVolFlow));
ShowContinueError(state,
format("For reference the zone design cooling air flow rate is {:.5R} [m3/s]",
state.dataSize->TermUnitFinalZoneSizing(state.dataSize->CurTermUnitSizingNum).DesCoolVolFlow));
ShowContinueError(state,
format("For reference the zone design minimum cooling air flow rate is {:.5R} [m3/s]",
state.dataSize->TermUnitFinalZoneSizing(state.dataSize->CurTermUnitSizingNum).DesCoolVolFlowMin));
int zoneNum = state.dataSize->TermUnitFinalZoneSizing(state.dataSize->CurTermUnitSizingNum).ZoneNum;
if (zoneNum > 0) {
int SizingInputNum =
Util::FindItemInList(state.dataHeatBal->Zone(zoneNum).Name, state.dataSize->ZoneSizingInput, &ZoneSizingInputData::ZoneName);
if (SizingInputNum == 0) {
SizingInputNum = 1;
}
if (state.dataSize->ZoneSizingInput.size() > 0 && state.dataSize->ZoneSizingInput(SizingInputNum).DesHeatMaxAirFlowFrac < 1.0) {
ShowContinueError(state,
format("Sizing:Zone Heating Maximum Air Flow Fraction = {:.5R}",
state.dataSize->ZoneSizingInput(SizingInputNum).DesHeatMaxAirFlowFrac));
ShowContinueError(state,
format("Sizing:Zone Heating Maximum Air Flow per Zone Floor Area = {:.5R} [m3/s/m2]",
state.dataSize->ZoneSizingInput(SizingInputNum).DesHeatMaxAirFlowPerArea));
ShowContinueError(state,
format("For reference the zone design maximum heating air flow rate is {:.5R} [m3/s]",
state.dataSize->TermUnitFinalZoneSizing(state.dataSize->CurTermUnitSizingNum).DesHeatVolFlowMax));
}
}
ShowContinueError(state, "Verify that the values entered are intended and are consistent with other components.");
}
if (TermUnitSizing(state.dataSize->CurTermUnitSizingNum).AirVolFlow > SmallAirVolFlow) {
if (this->DamperHeatingAction == Action::ReverseWithLimits) {
TermUnitSizing(state.dataSize->CurTermUnitSizingNum).ReheatAirFlowMult =
Expand Down
16 changes: 8 additions & 8 deletions tst/EnergyPlus/unit/Autosizing/WaterHeatingCoilUASizing.unit.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -176,12 +176,12 @@ TEST_F(AutoSizingFixture, WaterHeatingCoilUASizingGauntlet)
state->dataSize->ZoneSizingInput(1).ZoneNum = 1;
sizer.initializeWithinEP(*this->state, HVAC::cAllCoilTypes(HVAC::Coil_HeatingWater), "MyWaterCoil", printFlag, routineName);
sizedValue = sizer.size(*state, inputValue, errorsFound);
EXPECT_TRUE(errorsFound);
EXPECT_TRUE(state->dataSize->DataErrorsFound);
EXPECT_TRUE(sizer.dataErrorsFound);
EXPECT_ENUM_EQ(AutoSizingResultType::ErrorType1, sizer.errorType);
EXPECT_FALSE(errorsFound);
EXPECT_FALSE(state->dataSize->DataErrorsFound);
EXPECT_FALSE(sizer.dataErrorsFound);
EXPECT_ENUM_EQ(AutoSizingResultType::NoError, sizer.errorType);
EXPECT_TRUE(sizer.wasAutoSized);
EXPECT_NEAR(3.0, sizedValue, 0.01); // 0.1% of 3000 W capacity
EXPECT_NEAR(3000.0, sizedValue, 0.01); // 100% of 3000 W capacity
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@rraustad rraustad May 22, 2025

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If HW coil UA sizing fails with -2, the maximum UA limit is now used to size the coil. Previously the lower limit was used (because that's what gets returned from SolveRoot when that function fails with -2) and the coil was severely undersized (with associated error and a fatal).

state->dataWaterCoils->WaterCoil(1).InletAirTemp = 21.0;
state->dataSize->DataErrorsFound = false;
sizer.dataErrorsFound = false;
Expand Down Expand Up @@ -272,9 +272,9 @@ TEST_F(AutoSizingFixture, WaterHeatingCoilUASizingGauntlet)
EXPECT_ENUM_EQ(AutoSizingResultType::ErrorType1, sizer.errorType);
EXPECT_TRUE(sizer.wasAutoSized);
EXPECT_TRUE(errorsFound);
EXPECT_TRUE(state->dataSize->DataErrorsFound);
EXPECT_TRUE(sizer.dataErrorsFound);
EXPECT_NEAR(3.0, sizedValue, 0.01); // 0.1% of 3000 W capacity
EXPECT_FALSE(state->dataSize->DataErrorsFound);
EXPECT_FALSE(sizer.dataErrorsFound);
EXPECT_NEAR(3000.0, sizedValue, 0.01); // 100% of 3000 W capacity
state->dataWaterCoils->WaterCoil(1).InletAirTemp = 21.0;
state->dataSize->DataErrorsFound = false;
sizer.dataErrorsFound = false;
Expand Down
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